RFR: JDK-8301205: Port fdlibm log10 to Java

[Joe Darcy]

Restarting the port of FDLIBM to Java with the log10 method.

There are two port, the first a near-transliteration from C port to use as a test reference in

test/jdk/java/lang/StrictMath/FdlibmTranslit.java

and a more idiomatic Java port in 

src/java.base/share/classes/java/lang/FdLibm.java

First I debug the FdlibmTranslit port by running it against the C version. Once that is working, I copy the port into the java.lang.FdLibm.java and do a series of transformation to get the code closer to usual JDK style.

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Commit messages:
 - Reformat code some more.
 - Change to hex fp literals, misc updates.
 - Use more idiomatic style in ported FDLBIM code.
 - Merge branch 'master' into JDK-8301205
 - JDK-8301205: Port fdlibm log10 to Java

Changes: https://git.openjdk.org/jdk/pull/12242/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12242&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301205
  Stats: 222 lines in 4 files changed: 207 ins; 0 del; 15 mod
  Patch: https://git.openjdk.org/jdk/pull/12242.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12242/head:pull/12242

PR: https://git.openjdk.org/jdk/pull/12242